/Engine/Plugins/FX/Niagara/Source/Niagara/Public/NiagaraCompileHashVisitor.h
We don't usually want to save GUID's or pointer values because they have nondeterministic values. Consider a PostLoad upgrade operation that creates a new node. Each pin and node gets a unique ID. If you close the editor and reopen, you'll get a different set of values. One of the characteristics we want for compilation behavior is that the same graph structure produces the same compile results, so we only want to embed information that is deterministic. This method is for use when registering a pointer to an object that is serialized within the compile hash.
bool UpdateReference ( const TCHAR * InDebugName, const void * InObject )